The bioactive agents which are used in the inventive formulations are well known to the practitioner to which this invention pertains. Classes of bioactive agents contemplated by the inventive antibiotic formulations include anthelmintics, insecticides, acaricides, parasiticides, growth enhancers, and nonsteroidal anti-inflammatory drugs (NSAIDS). Specific classes of compounds which fall within these classes of bioactive agents include, for example, avermectins, milbemycins, nodulisporic acid and its derivatives, estrogens, progestins, androgens, substituted pyridylmethyl derivatives, phenylpyrazoles, and COX-2 inhibitors.
The avermectin and milbemycin series of compounds are potent anthelmintic and antiparasitic agents against a wide range of internal and external parasites. The compounds which belong to this series are either natural products or are semi-synthetic derivatives thereof. The structure of these two series of compounds are closely related and they both share a complex 16-membered macrocyclic lactone ring; however, the milbemycins do not contain the disaccharide substitutent in the 13-position of the lactone ring. The natural product avermectins are disclosed in U.S. Pat. No. 4,310,519 to Albers-Schonberg, et al., and the 22,23-dihydro avermectin compounds are disclosed in Chabala, et al., U.S. Pat. No. 4,199,569. For a general discussion of avermectins, which include a discussion of their uses in humans and animals, see “Ivermectin and Abamectin,” W. C. Campbell, ed., Springer-Verlag, N.Y. (1989). Naturally occurring milbemycins are described in Aoki et al., U.S. Pat. No. 3,950,360 as well as in the various references cited in “The Merck Index” 12th ed., S. Budavari, Ed., Merck & Co., Inc. Whitehouse Station, N.J. (1996). Semi-synthetic derivatives of these classes of compounds are well known in the art and are described, for example, in U.S. Pat. Nos. 5,077,308, 4,859,657, 4,963,582, 4,855,317, 4,871,719, 4,874,749, 4,427,663, 4,310,519, 4,199,569, 5,055,596, 4,973,711, 4,978,677,and 4,920,148.
European Patent Application 413,538 relates to an injectable formulation containing an avermectin compound and triacetin. European Patent Application 535,734 relates to an injectable formulation containing an avermectin compound and hydrogenated castor oil in a hydrophobic carrier such as triacetin. The formulations in both European Patent Applications are said to provide efficacy against external and internal parasites in animals only for up to 42 days. Neither of these applications suggests or teaches how to manipulate the composition of the formulation in order to achieve efficacy beyond 42 days.
Nodulisporic acid and its derivatives are a class of acaricidal, antiparasitic, insecticidal and anthelminitic agents known to a practitioner of the art. These compounds are used to treat or prevent infections in humans and animals. These compounds are described, for example, in U.S. Pat. No. 5,399,582 and WO 96/29073. Additionally, the compounds can be administered in combination with other insecticides, parasiticides, and acaricides. Such combinations include anthelminitic agents, such as those discussed above which include abamectin, doramectin, emamectin, eprinomectin, ivermectin, latidectin, lepimectin and selamectin, as well as other agents such as thiabendazole, febantel or morantel; phenylpyrazoles such as fipronil; and insect growth regulators such as lufenuron. Such combinations are also contemplated in the present invention.
Generally, all classes of insecticides are provided for in this invention. One example of this class include substituted pyridylmethyl derivatives such as imidacloprid. Agents of this class are described, for example, in U.S. Pat. No. 4,742,060 or in EP 892,060. It would be well within the skill level of the practitioner to decide which individual compound can be used in the inventive formulation to treat a particular infection of an insect.
Phenylpyrazoles are another class of insecticides which possess excellent insecticidal activity against all insect pests including blood-sucking pests such as ticks, fleas etc., which are parasites on animals. This class of agents kills insects by acting on the gamma-butyric acid receptor of invertebrates. Such agents are described, for example, in U.S. Pat. Nos. 5,567,429, 5,122,530, and EP 295,117. It would be well within the skill level of the practitioner to decide which individual compounds can be used in the inventive formulations.
Insect growth regulators are another class of insecticides or acaricides, which are also provided for in the inventive formulations. Compounds belonging to this group are well known to the practitioner and represent a wide range of different chemical classes. These compounds all act by interfering with the development or growth of the insect pests. Insect growth regulators are described, for example, in U.S. Pat. Nos. 3,748,356; 3,818,047; 4,225,598; 4,798,837; 4,751,225, as well as in EP 179,022 or U.K. 2,140,010. Again, it would be well within the skill level of the practitioner to decide which individual compounds can be used in the inventive formulation.
Estrogens, progestins, and androgens refers to classes of chemical compounds which are also well known to a practitioner in this art. In fact, estrogens and progestins are among the most widely prescribed drugs and are used, for example, alone or in combination for contraception or hormone replacement therapy in post menopausal women. Estrogens and progestins occur naturally or are prepared synthetically. This class of compounds also includes estrogens or progesterone receptor antagonists. Antiestrogens, such as tamoxifen and clomiphene, are used to treat breast cancer and infertility. Antiprogestives are used as contraceptives and anticancer drugs, as well as to induce labor or terminate a pregnancy.
The androgens and antiandrogens structurally related to the estrogens and progestins as they are also biosynthesized from cholesterol. These compounds are based on testosterone. Androgens are used for hypogonadism and promote muscle development. Antiandrogens are used, for example, in the management of hyperplasia and carcinoma of the prostate, acne, and male pattern baldness as well as in the inhibition of the sex drive in men who are sex offenders. Estrogen, progestins, and androgens are described, for example, in “Goodman & Gilman's The Pharmacological Basis of Therapeutics,” 10th ed., J. G. Hardman and Limbird, eds., Chapters 58 and 59, pp. 1597-1648, McGraw-Hill, N.Y. (2001) or in “Principles of Medicinal Chemistry,” ed., W. O. Foye, ed., Ch. 21, pp. 433-480, Lea & Febiger, Philadelphia (1989).
Estrogens, progestins and androgens are also used in animal husbandry as growth promoters for food animals. It is known in the art that compounds of these classes act as growth-promoting steroids in animals such as cattle, sheep, pigs, fowl, rabbits, etc. Delivery systems to promote the growth of animals are described, for example, in U.S. Pat. Nos. 5,401,507, 5,288,469, 4,758,435, 4,686,092, 5,072,716 and 5,419,910.
NSAIDS are well known in the art. The classes of compounds which belong to this group include salicylic acid derivatives, para-aminophenol derivatives, indole and indene acetic acids, heteroaryl acetic acids, arylpropionic acids, anthranilic acids (fenamates), enolic acids, and alkanones. NSAIDS exert their activity by interfering with prostaglandin biosynthesis by irreversibly or reversibly inhibiting cycloxygenase. Also included are COX-2 inhibitors which act by inhibiting the COX-2 receptor. Compounds of this group possess analgesic, antipyretic and nonsteroidal anti-inflammatory properties. Compounds belonging to these classes are described, for example, in Chapter 27 of Goodman and Gilman on pages 687-731 or in Chapter 22 of Foye on pages 503-530 as well as in U.S. Pat. Nos. 3,896,145; 3,337,570; 3,904,682; 4,009,197; 4,223,299; and 2,562,830, as well as the specific agents listed in The Merck Index.
While the individual bioactive agents are well-known in the art, there has been difficulties in the art to provide for a viable, easy to use, long acting injectable formulation containing these bioactive agents. Particularly problematic is the use of biologically acceptable polymers (e.g. poly(lactic-co-glycolic)acid copolymer (PLGA)) for injectable formulations which are useful for inducing long term release of the bioactive agent.
European Patent Application 0537559 concerns polymeric compositions having a thermoplastic polymer, rate modifying agent, water soluble bioactive material and water-miscible organic solvent. Upon exposure to an aqueous environment (e.g. body fluids) the liquid composition is capable of forming a biodegradable microporous, solid polymer matrix for controlled release of water soluble or dispersible bioactive materials over about four weeks. The thermoplastic polymer may be, among many listed, polylactide, polyglycolide, polycaprolactone or copolymers thereof, and is used in high concentration (45 to 50%). The rate modifying agent may be, among many others listed, glycerol triacetate (triacetin); however, only ethyl heptanoate is exemplified; and the amount of the rate modifying agent is no more than 15%.
Indeed, with respect to the patent literature, reference is made to:
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These documents tend to provide compositions that form a solid, gel or coagulated mass; for instance, a significant amount of polymer is contemplated in these documents, akin to European Patent Application 0537559, which makes them wholly unsuitable for injectable formulations.
Shah et al (J. Controlled Release, 1993, 27:139-147), as relating to formulations for sustained release of bioactive compounds containing various concentrations of poly (lactic-co-glycolic)acid copolymer (PLGA) dissolved in vehicles such as triacetin; Lambert and Peck (J. Controlled Release, 1995, 33:189-195), as a study of the release of protein from a 20% PLGA solution in N-methylpyrrolidone exposed to aqueous fluid; and Shivley et al (J. Controlled Release, 1995, 33:237-243), as a study of the solubility parameter of poly(lactide-co-glycolide)copolymer in a variety of solvents, and the in vivo release of naltrexone from two injectable implants (5% naltrexone in either 57% PLGA and 38% N-methylpyrrolidone or 35% PLGA and 60% N-methylpyrrolidone).
Controlled release of hydrophobic bioactive substance in vivo over an extended period of time is referred to in U.S. Pat. No. 6,733,767 which includes a polymer such as PLGA with a mixture of hydrophilic and lipophilic solvents. However, these formulations also suffer from problems of long term shelf stability and also with plugging of the needles used to inject the formulation.
An additional problem in the art is that some strains of ectoparasites and endoparasites have become resistant to antiparasitic agents administered in conventional formulations rendering them unsuitable for combating ectoparasites and endoparasites.
There is still a need in the art for long acting formulations which are suitable for injection and which have long term shelf stability. In addition, an ideal injectable formulation would not only be usable with smaller needle diameters but would have a long acting effect that would have a season long effect during the breeding perior for livestock mammals such as cattle, sheep and pigs or minimize the number of injections when applying to domestic mammals such as dogs and cats. It would also be beneficial if formulations could be developed which are able to treat ectoparasites and endoparasites which have become resistant to antiparasitic agents including macrocyclic lactones.
Citation or identification of any document in this application is not an admission that such document is available as prior art to the present invention.